Mokoena has been looking to secure a move to the PSL with the Students, although he and his current employers have been unable to agree a settlement dispute as the 31-year-old still has 12 months to run on his deal.
However, the two parties may be close to reaching an agreement as Mokoena, along with fellow African Kanu, were nowhere to be seen as the League One outfit returned from holiday on Monday.
Former Arsenal striker Kanu is also set to leave Pompey, although the Nigerian is also locked in a dispute with the team as he too has 12 months to run on his deal in England.
Mokoena would become Wits' fifth signing of the off-season, with Tlou Molekwane, Matthew Pattison, Ayo Oluwafemi and Thokozani Mshengu all having arrived at the club since the end of last season.